A Contribution to the Geologic History of the Floridian Plateau. 167 



with force enough to cause a distinct convexity of the surface during calm weather. 

 According to some authorities, it is difficult to row a small boat across the surface 

 above the spring on account of the outward movement of the water from above 

 t he i >rifice. 



These springs can scarcely be older than the age here assigned them, 

 otherwise they would have been filled by sediments. During this uplifl , 

 it appears the main drainage lines north of Lake Okeechobee were deter- 

 mined. It is known that the St. John's River channel has a depth of 65 

 feet below mean tide opposite Jacksonville. 1 



The precise date of the cutting of the submerged channel at the 

 mouth of St. John's River has not been determined and is here only 

 tentatively referred to the interval between the deposition of the Pliocene 

 and Pleistocene. 



That there was uplift in this interval is indisputable. The available 

 evidence does not suggest that it was over 200 feet. 



Accompanying this oscillation, either with the uplift or the subse- 

 quent depression, there was deformation. Pliocene fossils occur at a 

 depth of 150 feet in Lake Tohopekaliga and it is overlain by at least 100 

 feet of Pleistocene deposits— perhaps 150 feet. As the elevation of the 

 land surface at Kissimmee at the northern end of this lake is 60 feet, the 

 Pliocene is 90 feet below sea-level. The Pliocene at De Leon Springs 

 on the north is between 20 and 40 feet above sea-level ; along the Caloosa- 

 hatchee River 6 to 12 feet. The Pleistocene in the vicinity of Kissim- 

 mee fills a depression in the surface of the Pliocene to a depth of at least 

 100 feet, while it is thin along the Caloosahatchee and also at De Leon 

 Springs. The thickening of the deposits near Kissimmee seems to indi- 

 cate that a Pliocene syncline existed at the time of this deposition, and 

 that there was a very gentle anticlinal ridge, or swell, parallel to the 

 east coast, and a second similar gentle swell extending north from the 

 Caloosahatchee west of Kissimmee River, between it and Peace Creek. 

 Haines City occupied the northern end of this ridge. Between these 

 two gentle anticlines is the shallow syncline occupied by the Kissimmee 

 Valley. The eastern anticline was one of the agencies determining the 

 location of St. John's River. It seems probable that there was a third 

 gentle fold between Peace River and the west coast. 



These structural features have their axes parallel to the axis of the 

 Peninsula. Heilprin, Dall, and Matson and Clapp have all described the 

 folding of the Pliocene strata along the Caloosahatchee. Dall says con- 

 cerning these folds: 



As the river [Caloosahatchee] is ascended, a close scrutiny shows that it cuts 

 through a succession of gentle waves, gradually increasing in height, inland, whose 

 crests would show a general parallelism with the direction of the Peninsula of 

 Florida, or transverse to the average course of the river. Near the headwaters of 

 the river these waves of elevation rise above the level of the river at low water to 

 a height of perhaps 12 feet at most, and their individual length from one trough 

 to another may average about a quarter of a mile. Though insignificant as flexures, 

 thev are interesting as showing that a lateral as well as a vertical thrust has attended 

 the movements of the rocks in this part of the State, a fact which has been ques- 

 tioned. (U. S. Geol. Surv., Bull. 84, p. 143, 1892.) 



1 Matson and Clapp, op. cit., p. 172. 



